The present invention relates to apparatus and method for adhering two sheets of plate shaped matters such as optical disc substrates.
As is well known, for example, the following processes are adopted as a conventional method for mutually adhering two sheets of optical disc substrates with an adhesive.
First, the adhesive is circularly supplied onto an adhering surface of one of the two sheets of optical disc substrates, the one of the two sheets of the optical disc substrates is carried onto a lower disc absorption mechanism of an overlapping mechanism, is absorbed and held thereat, and with an adhering surface of the other of the two sheets of optical disc substrates faced downward, the other of the two sheets of the optical disc substrates is carried onto upper disc absorption mechanism in the overlapping mechanism, and adsorbed and held thereat.
Thereafter, a voltage is applied between the one optical disc substrate and the other optical disc substrate to make the one optical disc substrate and the other optical disc substrate approach to each other and the two optical disc substrates are overlapped with each other. When a distance between the two optical disc substrates reaches to a set inter-substrate distance, the voltage application is stopped so that the lower disc absorption mechanism and the upper disc absorption mechanism are released from the absorption and holding.
Then, the two sheets of mutually overlapped optical disc substrates are carried to a spinner. Then, the spinner is rotated at a high speed and the adhesive is widened to a predetermined region. An ultraviolet ray is, then, radiated on the optical disc substrate so as to cure an adhesive layer.
When the two sheets of optical disc substrates are mutually overlapped with each other via the adhesive, the two optical disc substrates are mutually approached to each other. As a distance between two optical disc substrates becomes shorter, an influence of voltage application becomes so large that a summit portion of the adhesive is tapered and a contact area between the adhesive and the other optical disc substrate becomes very small at an instantaneous time when the adhesive is brought in contact with the other disc substrate. This can mutually overlap the two optical disc substrates without development in air bubbles thereon.
In the above-described conventional art, in order to shorten a required time of adhering step, a velocity of approaching two sheets of optical disc substrates 1 and 2 maybe quickened. As the velocity is increased, the summit portion of adhesive 5 cannot sufficiently be tapered. The contact area between adhesive 5 and the other optical disc substrate becomes large. Consequently, air bubbles tend to be easy to be generated.
In this case, the increase in the voltage value to be applied causes the electric field to be increased. Hence, the summit portion of the adhesive can be tapered. However, if the two sheets of optical disc substrates mutually approach to each other, a discharge phenomenon occurs between the two sheets of optical disc substrates. This discharge phenomenon causes a partial breakage of a metal reflective film formed on a recording sheet, causes several pits to be damaged, and a reliability of data recording is reduced.
In addition, after the adhesive is applied over a whole periphery with a predetermined radius of the one optical disc substrate, it is necessary to mutually approach the two sheets of optical disc substrates, to widen a liquid film of the adhesive between an inner peripheral direction and an outer peripheral direction, and to stabilize a liquid film to a degree such that no problem occurs when the two sheets of optical disc substrates are carried. However, a continuous application of voltage causes the adhesive to be deteriorated and a reliability is reduced. The above-described problems could occur in such a plate shaped matter as a glass plate, a lens, or the like other than the optical disc substrates.
It is an object of the present invention to provide plate shaped matter adhering apparatus and plate shaped matter adhering method which can shorten a whole time duration for which the two sheets of optical disc substrates are adhered together when two sheets of plate shaped matters are mutually approached to each other without development of air bubbles and in which an adhesive is not deteriorated without occurrence in discharge between two sheets of optical disc substrates.
To achieve the above-described object, according to the present invention, a relative velocity between first and second plate shaped matters at a time point immediately after the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter is lower than the relative velocity at a time point immediately before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter and a voltage is applied between the first plate matter and the second plate shaped matter at a time point before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter and an alternating current voltage is applied between the first plate shaped matter.
That is to say, according to the present invention defined in a first embodiment of the invention, there is provided a plate shaped matter adhering apparatus which adheres between a first plate shaped matter and a second plate shaped matter together via an adhesive and cures the adhesive, the plate shaped matter adhering apparatus comprising: plate shaped matter moving means for moving the first plate shaped matter and the second plate shaped matter to approach to each other with the adhesive applied onto the second plate shaped matter while the first plate shaped matter is faced against the second plate shaped matter; velocity controlling means for controlling a relative velocity of one of the first and second plate shared matters to the other of the first and second plate shared matters and controlling the plate shaped matter moving means in such a manner that the relative velocity immediately after and at a time point at which the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter is slower than that immediately before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter; and voltage applying means for applying voltage between the first plate shaped matter and the second plate shaped matter before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter.
According to the invention defined in a second embodiment of the invention, there is provided a plate shaped matter adhering apparatus as defined in the first embodiment, wherein the adhering apparatus further comprises distance detecting means for detecting a distance between the first plate shaped matter and the second plate shaped matter and estimates a time point immediately before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter on the basis of the distance detected by the distance measuring means.
According to the invention defined in a third embodiment of the invention, there is provided a plate shaped matter adhering apparatus as defined in the second embodiment, wherein the distance between the first plate shaped matter and the second plate shaped matter at the time point immediately before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter is equal to or shorter than 5 mm and, preferably, is equal to or shorter than 2 mm.
According to the invention defined in a fourth embodiment of the invention, there is provided a plate shaped matter adhering apparatus as defined in the first embodiment, wherein the adhering apparatus further comprises time elapsed detecting means for detecting a time elapsed from a predetermined timing and estimates a time point immediately before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter on the basis of the time detected by the time elapsed detecting means.
According to the invention defined in a fifth embodiment of the invention, there is provided a plate shaped matter adhering apparatus for a plate shaped matter as defined in the first embodiment, wherein the relative velocity at a time point immediately before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter is equal to or higher than 25 mm/second and, preferably, is equal to or higher than 50 mm/second.
According to the invention defined in a sixth embodiment of the invention, there is provided a plate shaped matter adhering apparatus as defined in the first embodiment, wherein the relative velocity at a time point immediately after the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter is equal to or lower than 10 mm/second and, preferably, is equal to or higher than 5 mm/second.
According to the invention defined in a seventh embodiment of the invention, there is provided a plate shaped matter adhering apparatus which adheres between a first plate shaped matter and a second plate shaped matter together via an adhesive and cures the adhesive, the plate shaped matter adhering apparatus comprising: plate shaped matter moving means for moving the first plate shaped matter and the second plate shaped matter to approach to each other with the adhesive applied onto the first plate shaped matter and onto the second plate shaped matter while the first plate shaped matter is faced against the second plate shaped matter; velocity controlling means for controlling a relative velocity of one of the first and second plate shaped matters to the other of the first and second plate shaped matters and controlling the plate shaped matter moving means in such a manner that the relative velocity immediately after and at a time point at which the adhesive applied onto the first plate shaped matter is brought in contact with the adhesive applied onto the second plate shaped matter is slower than that immediately before the adhesive applied onto the first plate shaped matter is brought in contact with the adhesive applied onto the second plate shaped matter; and voltage applying means for applying voltage between the first plate shaped matter and the second plate shaped matter before the adhesive applied onto the first plate shaped matter is brought in contact with the adhesive applied onto the second plate shaped matter.
According to the invention defined in an eighth embodiment of the invention, there is provided a plate shaped matter adhering apparatus as claimed in any one of the preceding first through seventh embodiments, wherein the voltage application means is turned off after the adhesive is brought in contact with the other adhesive.
According to the invention defined in a ninth embodiment of the invention, there is provided a plate shaped matter adhering method in which a first plate shaped matter and a second plate shaped matter are adhered together via an adhesive and the adhesive is cured, the plate shaped matter adhering method comprising: plate shaped matter moving step for moving the first plate shaped matter and the second plate shaped matter to approach to each other with the adhesive applied onto the second plate shaped matter while the first plate shaped matter is faced against the second plate shaped matter; velocity controlling step for controlling a relative velocity of one of the first and second plate shaped matters to the other of the first and second plate shaped matters in such a manner that the relative velocity immediately after and at a time point at which the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter is slower than that immediately before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter; and voltage applying step for applying voltage between the first plate shaped matter and the second plate shaped matter before the adhesive applied onto the second plate shaped matter is brought in contact with the first plate shaped matter.
According to the invention defined in a tenth embodiment of the invention, there is provided a plate shaped matter adhering method in which a first plate shaped matter and a second plate shaped matter are adhered together via an adhesive and the adhesive is cured, the plate shaped matter adhering method comprising: plate shaped matter moving step for moving the first plate shaped matter and the second plate shaped matter to approach to each other with the adhesive applied onto the first plate shaped matter and onto the second plate shaped matter while the first plate shaped matter is faced against the second plate shaped matter; velocity controlling step for controlling a relative velocity of one of the first and second plate shaped matters to the other of the first and second plate shaped matters and controlling the plate shaped matter moving means in such a manner that the relative velocity immediately after and at a time point at which the adhesive applied onto the first plate shaped matter is brought in contact with the adhesive applied onto second plate shaped matter is slower than that immediately before the adhesive applied onto the first plate shaped matter is brought in contact with the adhesive applied onto the second plate shaped matter; and voltage applying step for applying voltage between the first plate shaped matter and the second plate shaped matter immediately before the adhesive applied onto the first plate shaped matter is brought in contact with the adhesive applied onto the second plate shaped matter.
According to the invention defined in an eleventh embodiment of the invention there is provided a plate shaped matter adhering method as defined in the ninth embodiment, wherein, when the one adhesive is brought in contact with the other plate shaped matter, the application of the voltage is stopped.